The present invention relates to protractors, squares and gauges for measuring and setting angles between surfaces on machinery, protractors and squares.
It is frequently necessary to adjust the relative angular position of two machine surfaces or of a machine surface with respect to a cutting tool utilized in the machine. While metalworking machinery and industrial quality woodworking machinery frequently include built-in scales or read-out devices which permit such angular positioning to be accomplished reproducibly and with great precision, most woodworking machinery lacks accurate angle setting components. Nevertheless, it frequently is desirable to set woodworking machinery to predetermined angles with substantial precision. For instance, wood objects are frequently fabricated of multiple identical segments with mitered joints. Perhaps the most common example of such objects are rectangular picture frames, but frames, clock faces, turning blanks, and a wide variety of other objects are often fabricated utilizing various numbers of segments. Frequently used numbers of segments are four, five, six, eight and twelve segments.
In order to prepare material for constructing such structures, it is typically necessary to set movable members of a woodworking tool such as a table saw, band saw, radial arm saw, or jointer in order accurately to machine a desired angle on the wood components. Best known among these angles is the 45.degree. angle required in order to make mitered joints on a square or rectangular picture frame or other four-sided structure. Accordingly, because of its frequent use, gauges and miter squares including a 45.degree. angle are widely available. Other less commonly used angles are required, however, in order to set-up a woodworking tool to machine stock for objects fabricated from other multiples of identical segments. This is sometimes accomplished using a machinist's vernier bevel protractor, but this is an expensive instrument often unavailable in a woodworking shop. Typically, the best tools available in a woodworking shop are the rule and protractor head of a combination square used with a sliding bevel gauge. These tools are not well adapted to this application, however, must be set for each desired angle with care and are difficult to use with high accuracy. Paradoxically, although 45.degree. angle gauges and squares are readily available, the tool set-up accuracy required in order to machine components for multi-segment fabrications having more than four segments is greater, rather than less, than that required for a four-segment object, because any error in the angle machined on components is multiplied by the number of components. In short, the more sides involved, the greater the need for accuracy.
Additional problems presented in utilizing previously-available gauges for tool set-up include the difficulty of using many such gauges in an upright position, as distinguished from lying flat on a horizontal table of the machine or tool being adjusted. Many existing protractors and gauges will not remain upright without support in the position necessary, for instance, to set a table saw or radial arm saw blade angle.
In accordance with the convention typically employed in tool-related terminology, reference herein to the "angle" a surface forms to another surface or a designated line means the angle formed between (a) a first imaginary line on that surface and normal to the surface edge and (b) the designated line or an imaginary line on the other surface also normal to the surface edge and intersecting the first imaginary line.